1. Field of the Invention
The invention relates in general to a watercraft, and in particular to a marine jet propulsion system for a watercraft, and more particularly to an impeller for a jet propulsion device.
2. Description of the Related Art
Personal watercraft have become increasingly popular in recent years. Jet propulsion devices commonly power these type of watercraft and include a motor driven impeller. The impeller operates within a water duct of the jet propulsion device. The rotating impeller draws in water through a water intake opening on the underside of the watercraft's hull and into the intake duct. The impeller forces the water through a discharge nozzle to form a jet of water. This water jet propels the watercraft.
One problem particular to impeller constructions is that, due to a variety of reasons, cavitation or precipitation of gaseous bubbles or vapor can occur. One reason cavitation may occur is due to the pressure variations attendant to the actual rotation of the impeller. These vapors or bubbles can then implode on the impeller surface, thereby possibly causing impeller erosion. Disadvantageously, this can affect performance and shorten the life of the impeller.